Clozapine Diminishes Suicidal Behavior: A Retrospective Evaluation of Clinical Records

Objective: To test the antisuicidal effect of clozapine, taking into consideration some potentially confounding variables.

Method: A retrospective evaluation was conducted of the clinical charts of 94 inpatients treated continuously with clozapine for at least 6 weeks between 1962 and 1994. In a mirror design, a period of continuous clozapine treatment (mean duration of 15 months) was compared with a pre-clozapine period of equal length, and in 17 patients also with a post-clozapine period, with regard to suicidal behavior. The role of variables such as staying in a protective hospital milieu and receiving treatment with typical neuroleptics and antidepressants was considered.

Results: The rate of suicidal behavior was 28% (26/94) in the pre-clozapine period, 3% (3/94) in the clozapine period, and 18% (3/17) in the post-clozapine period, the corresponding figures for serious suicidal behavior requiring medical attention being 12% (11/94), 1% (1/94), and 12% (2/17), respectively. The odds ratios were 11.6 (95% CI = 3.4 to 39.9) and 12.3 (95% CI = 1.6 to 97.5) for suicidal and serious suicidal behavior, respectively, in favor of the clozapine period in comparison with the pre-clozapine period. Staying in the hospital was associated with reduction in suicidal behavior. The antisuicidal effect of clozapine possibly disappears at doses that are too low.

Conclusion: Clozapine diminishes the frequency of suicidal behavior including serious suicidal acts, regardless of comedication with antidepressants. In the protective hospital milieu, this effect is less pronounced, and it disappears after clozapine discontinuation.